Features under consideration for HTML5.1, though not necessarily mentioned in the first draft, include improvements to video captioning and fast seeking; better forms, including input modes and autocomplete; spell checking; better image accessibility; and more powerful iframes, for embedding documents, a W3C representative said. One intention for Canvas 2D Level 2, meanwhile, is that it would work better on high-resolution displays.

W3C hopes to finalize HTML5.1 as an official "W3C Recommendation" in 2016; no date is set yet for finalizing Canvas 2D Level 2. Final adoption of HTML5 as an W3C Recommendations, meanwhile, is anticipated in 2014. Canvas 2D could become official in 2013.

One issue that continues to be a thorn in the side for HTML5 is the lack a standard video codec, with W3C not having found a suitable one that meets the organization's royalty-free requirements. The organization has considered such codecs as H.264 and Google's VP8, which Google said is in fact royalty-free. H.264 is administered by patent pool packager MPEG LA. "It is my view that it would be desirable for MPEG LA to make [patents pertaining to H.264] available on a royalty-free basis," W3C CEO Jeff Jaffe said. MPEG LA offers H.264 royalty-free only in certain cases.

Moving HTML5 to feature-completeness was viewed as one milestone of many and important in marching the Web platform forward, analyst Al Hilwa, of IDC, said. But he cited mobile devices and mobile applications as a challenge for HTML5. "Native platforms will continue to be the dominant platforms for the most complex apps that wish to take advantage of the latest device features or where performance is top criteria," he said. "HTML5 will gain share for a broad base of other apps not having such demands."